In the international standard classification, iso rh involves: Fasteners for aerospace construction.
Association Francaise de Normalisation, iso rh
NF L22-441:1993 HEXAGONAL NUTS. REDUCED HEIGHT. REDUCED ACROSS FLATS. ISO RH THREAD. 4H5H OR 5H TOLERANCE CLASS ACCORDING TO DIAMETER.
NF L22-443:1993 HEXAGONAL NUTS. REDUCED HEIGHT. REDUCED ACROSS FLASTS WITH LOCKING HOLES. ISO RH THREAD. 4H5H OR 5H TOLERANCE CLASS ACCORDING TO DIAMETER.